This invention relates generally to a method and apparatus for charging rechargeable batteries.
The battery packs for portable power tools, outdoor tools, and certain kitchen and domestic appliances usually have several cells disposed in series. Users typically remove the battery packs from the battery charger after completion of the fast charging process, but before sufficient equalizing charge has been provided to the battery for equalizing the capacities of the various cells. Over time, the cell capacities become further out of balance, with some cells becoming significantly lower in capacity relative to the others.
The battery pack is typically usable until the charge in the lower-capacity cells is depleted. Accordingly, the user perceives that the capacity of the battery pack and/or battery life is the decreased and may incorrectly attribute this to a xe2x80x9cmemoryxe2x80x9d problem. The user may also perceive that the battery pack may be defective.
It is preferable to provide a method and apparatus that enables the user to equalize, or xe2x80x9crefresh,xe2x80x9d the cell capacities, in order to restore battery pack capacity.
In accordance with the present invention, a method for charging a rechargeable battery pack is proposed. The charging method includes providing a charger having first and second charging processes, and manually selecting one of the first and second charging processes. The charging method may include a step for indicating status or end of the selected one charging process. The first charging process may include the steps of providing a fast charging current, indicating end of the fast charging current and providing an equalization current. The second charging process may include the steps of providing a fast charging current, subsequently providing an equalization current and indicating end of equalization current. The first or second charging processes may also include a temperature checking step.
Also disclosed herein is a battery charging apparatus comprising a charger for charging a battery and having first and second charging processes, and a switch connected to the charger for manually selecting one of the first and second charging processes. The charger may include a microprocessor. Further, the apparatus may include a display output and/or sound output connected to the charger. The display output and/or sound output may indicate status or end of the selected one charging process. The display output may comprise a light bulb, a light emitting diode and/or a liquid crystal display. The sound output may comprise a speaker and/or a piezo-electric device.
Additional features and benefits of the present invention are described, and will be apparent from, the accompanying drawings and the detailed description below.